This invention relates to highly active and stable ruthenium and osmium metal carbene complex compounds, their synthesis and use as catalysts for olefin metathesis reactions.
Transition-metal catalyzed Cxe2x80x94C bond formation via olefin metathesis is of considerable interest and synthetic utility. Initial studies in this area were based on catalytically active mixtures consisting of transition-metal chlorides, oxides or oxychlorides, cocatalysts such as EtAlCl2 or R4Sn, and promoters including O2, EtOH or PhOH. For example, WCl6/EtAlCl2/EtOH 1:4:1. These systems catalyze olefin metathesis reactions, however their catalytic centers are ill-defined and systematic control of their catalytic activity is not possible.
Recent efforts have been directed towards the development of well-defined metathesis active catalysts based on transition metal complexes. The results of research efforts during the past two decades have enabled an in-depth understanding of the olefin metathesis reaction as catalyzed by early transition metal complexes. In contrast, the nature of the intermediates and the reaction mechanism for Group VIII transition metal catalysts have remained elusive. In particular, the oxidation states and ligation of the ruthenium and osmium metathesis intermediates are not known.
Group VIII transition metal olefin metathesis catalysts, specifically ruthenium and osmium carbene complexes, have been described in U.S. Pat. Nos. 5,312,940 and 5,342,909 and U.S. patent application Ser. Nos. 08/282,826 and 08/282,827, all of which are incorporated herein by reference. The ruthenium and osmium carbene complexes disclosed in these patents and applications are of the general formula 
where M is ruthenium or osmium, X and X1 are anionic ligands, and L and L1 are neutral electron donors. U.S. Pat. Nos. 5,312,940 and 5,342,909 disclose specific vinyl alkylidene ruthenium and osmium complexes and their use in catalyzing the ring opening metathesis polymerization (xe2x80x9cROMPxe2x80x9d) of strained olefins. In all of the specific alkylidene complexes disclosed in these patents, R1 is hydrogen and R is either a substituted or unsubstituted vinyl group. For example, a preferred vinyl alkylidene complex disclosed in these patents is 
where Ph is phenyl.
U.S. patent application Ser. Nos. 08/282,826 and 08/282,827 disclose specific vinyl alkylidene ruthenium and osmium complexes and their use in catalyzing a variety of metathesis reactions. The catalysts disclosed in these applications have specific neutral electron donor ligands L and L1; namely, phosphines in which at least one substituent is a secondary-alkyl or cycloalkyl group. As in the above U.S. patents, in all of the specific alkylidene complexes disclosed in the patent applications, R1 is hydrogen and R is either a substituted or unsubstituted vinyl group. For example, a preferred vinyl alkylidene complex disclosed in these patent applications is 
where Cy is cyclohexyl.
Although the vinyl alkylidene complexes disclosed in the above patents and patent applications exhibit high metathesis activity and remarkable stability towards functional groups there are at least two drawbacks to these complexes as metathesis catalysts. First, the preparation of the vinyl alkylidene complexes requires a multi-step synthesis; and second, the vinyl alkylidene complexes have relatively low initiation rates. Both of these aspects of the vinyl alkylidene complexes are undesirable for their use as metathesis catalysts. The multi-step synthesis may be time consuming and expensive and may result in lower product yields. The low initiation rate may result in ROMP polymers with a broad molecular weight distribution and prolonged reaction times in ring closing metathesis (xe2x80x9cRCMxe2x80x9d) reactions.
For the reasons discussed above, there is a need for well-defined metathesis active catalysts that have the following characteristics: first, they are stable in the presence of a wide variety of functional groups; second, they can catalyze a variety of metathesis reactions including the metathesis of acyclic and unstrained cyclic olefins; third, they have a high initiation rate; and fourth, they are easily prepared. Furthermore, there is a need for olefin metathesis catalysts that can catalyze the ROMP of strained and unstrained cyclic olefins to yield polymers of very low polydispersity (i.e., PDI≈1.0) and that can catalyze the RCM of acyclic dienes with short reaction times.
The present invention meets the above needs and provides well-defined ruthenium and osmium carbene compounds that are stable in the presence of a variety of functional groups and can be used to catalyze olefin metathesis reactions on unstrained cyclic and acyclic olefins. The compounds of the present invention are highly active in metathesis reactions and have high initiation rates.
In one embodiment of the present invention, the ruthenium and osmium carbene compounds have the formula 
where M may be Os or Ru; R1 is hydrogen; X and X1 may be different or the same and are any anionic ligand; L and L1 may be different or the same and are any neutral electron donor; and R may be hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl.
The ruthenium and osmium carbene complexes of the present invention are stable in the presence of a variety of functional groups. A consequence of this is that the alkyl and aryl R group may contain one or more functional groups including alcohol, thiol, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, and halogen groups.
R is preferably hydrogen, C1-20 alkyl, or aryl. The C1-20 alkyl may optionally be substituted with one or more aryl, halide, hydroxy, C1-20 alkoxy, or C2-20 alkoxycarbonyl groups. The aryl may optionally be substituted with one or more C1-20 alkyl, aryl, hydroxyl, C1-5 alkoxy, amino, nitro, or halide groups.
L and L1 are preferably phosphines of the formula PR3R4R5, where R3 is a secondary alkyl or cycloalkyl, and R4 and R5 are aryl, C1-10 primary alkyl, secondary alkyl, or cycloalkyl. R4 and R5 may be the same or different.
L and L1 are are most preferably the same and are xe2x80x94P(cyclohexyl)3, xe2x80x94P(cyclopentyl)3, or xe2x80x94P(isopropyl)3.
X and X1 are most preferably the same and are chlorine.
In another embodiment of the present invention, the ruthenium and osmium carbene compounds have the formula 
where M may be Os or Ru; X and X1 may be different or the same and are any anionic ligand; L and L1 may be different or the same and are any neutral electron donor; and R9 and R10 may be different or the same and may be hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl. The R9 and R10 groups may optionally include one or more of the following functional groups: alcohol, thiol, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, and halogen groups
The ruthenium and osmium carbene compounds of the present invention may be used to catalyze olefin metathesis reactions including, but not limited to, ROMP, RCM, depolymerization of unsaturated polymers, synthesis of telechelic polymers, and olefin synthesis.
In the ROMP reaction, a compound according to the present invention is contacted with a cyclic olefin to yield a ROMP polymer product. In the RCM reaction, a compound according to the present invention is contacted with a diene to yield a ring-closed product. In the depolymerization reaction, a compound according to the present invention is contacted with an unsaturated polymer in the presence of an acyclic olefin to yield a depolymerized product. In the synthesis of telechelic polymers, a compound according to the present invention is contacted with a cyclic olefin in the presence of an xcex1,xcfx89-difunctional olefin to yield a telechelic polymer. In the olefin synthesis reaction, a compound according to the present invention is contacted with one or two acyclic olefins to yield self-metathesis or cross-metathesis olefin products.
Since the ruthenium and osmium carbene compounds of the present invention are stable in the presence of a variety of functional groups, the olefins involved in the above reactions may optionally be substituted with one or more functional groups including alcohol, thiol, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, and halogen groups.
The above reactions may be carried out in aqueous, protic, or organic solvents or mixtures of such solvents. The reactions may also be carried out in the absence of a solvent. The reactants may be in the gas phase or liquid phase.
The ruthenium and osmium carbene compounds of the present invention may be synthesized using diazo compounds, by neutral electron donor ligand exchange, by cross metathesis, using acetylene, using cumulated olefins, and in a one-pot method using diazo compounds and neutral electron donors.